Atomic layer deposition methods

ABSTRACT

The invention includes an atomic layer deposition method of forming a layer of a deposited composition on a substrate. The method includes positioning a semiconductor substrate within an atomic layer deposition chamber. On the substrate, an intermediate composition monolayer is formed, followed by a desired deposited composition from reaction with the intermediate composition, collectively from flowing multiple different composition deposition precursors to the substrate within the deposition chamber. A material adheres to a chamber internal component surface from such sequentially forming. After such sequentially forming, a reactive gas flows to the chamber which is different in composition from the multiple different deposition precursors and which is effective to react with such adhering material. After the reactive gas flowing, such sequentially forming is repeated. Further implementations are contemplated.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 10/863,048, filed Jun. 7, 2004, entitled “AtomicLayer Deposition Methods”, naming Demetrius Sarigiannis, Garo J.Derderian, Cern Basceri, Gurtej S. Sandhu, F. Daniel Gealy and Chris M.Carlson as inventors, which is a continuation application of U.S. patentapplication Ser. No. 10/222,282, filed Aug. 15, 2002, entitled “AtomicLayer Deposition Methods”, naming Demetrius Sarigiannis, Garo J.Derderian, Cem Basceri, Gurtej S. Sandhu, F. Daniel Gealy and Chris M.Carlson as inventors, now U.S. Pat. No. 6,753,271, issued Jun. 22, 2004,the disclosures of which are incorporated by reference.

TECHNICAL FIELD

This invention relates to atomic layer deposition methods.

BACKGROUND OF THE INVENTION

Semiconductor processing in the fabrication of integrated circuitrytypically includes the deposition of layers on semiconductor substrates.One such method is atomic layer deposition (ALD) which involves thedeposition of successive monolayers over a substrate within a depositionchamber typically maintained at subatmospheric pressure. With typicalALD, successive mono-atomic layers are adsorbed to a substrate and/orreacted with the outer layer on the substrate, typically by successivefeeding of different deposition precursors to the substrate surface.

Atomic layer depositions are typically conducted within chambers orreactors which retain a single substrate upon a wafer holder orsusceptor. The chambers include internal walls and other internalcomponents which can undesirably have deposition product depositedthereupon in addition to the substrate. One existing method ofprotecting or preserving the internal chamber walls and other componentsis to shield such from the deposition material with one or moreremovable liners or shields. The liners might be received immediatelyadjacent or against the internal chamber walls or other surfaces.Alternately, the liners might be displaced from the wall or othersurfaces, thereby defining an appreciably reduced volume chamber, orsubchamber, within which the substrate is received for deposition. Oneadvantage of using liners and shields is that they can be periodicallyreplaced with new or cleaned liners, thereby extending the life of thedeposition chambers and components therein. Further and regardless, thespent liners and shields can typically be removed and replaced much morequickly than the time it would take to clean the internal chamber wallsand other components at given cleaning intervals.

An exemplary ALD method includes feeding a single vaporized precursor toa deposition chamber effective to form a first monolayer over asubstrate received therein. Thereafter, the flow of the first depositionprecursor is ceased and an inert purge gas is flowed through the chambereffective to remove any remaining first precursor which is not adheringto the substrate from the chamber. Subsequently, a second vaporprecursor different from the first is flowed to the chamber effective toform a second monolayer on/with the first monolayer. The secondmonolayer might react with the first monolayer. Additional precursorscan form successive monolayers, or the above process can be repeateduntil a desired thickness and composition layer has been formed over thesubstrate.

It is a desired intent or effect of the purging to remove unreacted gasor reaction by-products from the chamber to provide a clean reactivesurface on the substrate for the subsequent precursor. In the context ofthis document, a reaction by-product is any substance (whether gas,liquid, solid or mixture thereof which results from reaction of anydeposition precursor flowing to the chamber and that is not desired tobe deposited on the substrate. Further in the context of this document,an intermediate reaction by-product or reaction intermediate by-productis a reaction by-product formed by less than desired complete reactionof a precursor to form a desired monolayer on the substrate. Where thereis a great degree of varying topography and/or there are high aspectratio features on the substrate, it can be difficult to move theunreacted gases or reaction by-products from deep within openings forultimate removal from the chamber. Further, certain reactionby-products, particularly intermediate reaction by-products, may not begaseous and may not completely react to form gaseous reactionby-products in the typical short precursor pulse times. Accordingly, thepurge gas pulse may not be effective or sufficient in removing suchintermediate reaction by-products from the substrate and chamber.

For example, consider that in an atomic layer deposition of titaniumnitride using TiCl₄ and NH₃, the desired deposition product is TiN withHCl gas being the desired principle gaseous by-product. Consider alsothat there might be reaction intermediate by-products which might, evenif gaseous, be difficult to remove from substrate openings. Further, ifcertain reaction intermediate by-products are solid and/or liquid phaseprior to HCl formation, complete removal can be even more problematicwhere less than complete reaction to TiN and HCl occurs.

Consider also the atomic layer deposition of Al₂O₃ usingtrimethylaluminum (TMA) and ozone as alternating deposition precursors.Apparently in such deposition, achieving an effective ozone precursorfeed can be somewhat of a challenge due to the limited lifetime of ozonewithin the chamber. Specifically, an ozone molecule is in an inherentlyunstable, reactive form of oxygen which can rapidly dissociate and/orcombine with another ozone molecule to form three O₂ molecules.Regardless, a desired goal in the ozone feed is to result in oxygenatoms from the O₃ bonding to the surface of the substrate with O₂ as thereaction by-product which is driven off. Of course, the O₂ which formsdeep within openings on the substrate has to be removed therefrom whilemore O₃ needs to get into the openings to desirable form a completemonolayer of oxygen atoms adhered and projecting from the substrate. Inother words, the O₂ which forms is trying to get out while more O₃ isdesirably trying to get in.

While the invention was motivated in addressing the above issues andimproving upon the above-described drawbacks, it is in no way solimited. The invention is only limited by the accompanying claims asliterally worded (without interpretative or other limiting reference tothe above background art description, remaining portions of thespecification or the drawings) and in accordance with the doctrine ofequivalents.

SUMMARY

The invention includes an atomic layer deposition method of forming alayer of a deposited composition on a substrate. The method includespositioning a semiconductor substrate within an atomic layer depositionchamber. On the substrate, an intermediate composition monolayer isformed, followed by a desired deposited composition from reaction withthe intermediate composition, collectively from flowing multipledifferent composition deposition precursors to the substrate within thedeposition chamber. A material adheres to a chamber internal componentsurface from such sequential forming. After such sequential forming, areactive gas flows to the chamber which is different in composition fromthe multiple different deposition precursors and which is effective toreact with such adhering material. After the reactive gas flowing, suchsequential forming is repeated.

Further implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic depiction of flow versus time of one atomiclayer deposition process in accordance with an aspect of the invention.

FIG. 2 is a diagrammatic depiction of flow versus time of one atomiclayer deposition process in accordance with an aspect of the invention.

FIG. 3 is a diagrammatic depiction of flow versus time of one atomiclayer deposition process in accordance with an aspect of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

An atomic layer deposition method in accordance with an aspect of theinvention includes positioning a semiconductor substrate within anatomic layer deposition chamber. In the context of this document, theterm “semiconductor substrate” or “semiconductive substrate” is definedto mean any construction comprising semiconductive material, including,but not limited to, bulk semiconductive materials such as asemiconductive wafer (either alone or in assemblies comprising othermaterials thereon), and semiconductive material layers (either alone orin assemblies comprising other materials). The term “substrate” refersto any supporting structure, including, but not limited to, thesemiconductive substrates described above.

An intermediate composition monolayer is formed on the substrate fromone or more deposition precursors flowed to the substrate within thedeposition chamber. Then, one or more different composition depositionprecursors is flowed to the substrate within the deposition chambereffective to react with the first monolayer and form a monolayercomprising a desired deposited composition of the ultimate layer beingformed, with “desired” herein referring to at least at this point intime with respect to the preferred method. In other words, suchdeposited layer might be subsequently annealed, implanted, exposed toplasma, or otherwise processed in a manner which does not significantlymodify its overall composition. Any deposition precursor gases arecontemplated whether existing or yet-to-be developed. By way of exampleonly where a desired ultimate deposition product or layer is TIN,exemplary different composition precursors include TiCl₄ or NH₃ todeposit a TiN comprising layer. Further by way of example only where theultimate layer or product being formed is to be Al₂O₃, exemplarydifferent composition deposition precursors include trimethylaluminumand ozone. Further by way of example only, an exemplary first monolayerintermediate composition utilizing TiCl₄ would include titanium or atitanium complex, whereas with respect to NH₃ such would at leastinclude nitrogen. With respect to trimethylaluminum, the first monolayerintermediate composition would include an aluminum complex, and withozone typically adhered oxygen atoms. Any suitable temperature,pressure, flow rate or other operating parameters, with or withoutplasma, can be selected and optimized by the artisan, of course, with noparticular set of the same being preferred or constituting a part of theinvention.

By way of example only, FIG. 1 depicts an exemplary plot of flow rateversus time of but one process in accordance with an aspect of theinvention. A first precursor gas is flowed to the substrate within theatomic layer deposition chamber effective to form a first monolayer onthe substrate. Such is designated by a precursor flowing P1. Afterforming the first monolayer of intermediate composition on thesubstrate, a second precursor gas, different in composition from thefirst precursor gas, is flowed to the substrate within the depositionchamber effective to react with the first monolayer and form a monolayercomprising the desired deposited composition. Such second precursor gasflowing is designated by P2. The particular lengths and rates of therespective flowings, and the times therebetween, can also be optimizedby the artisan, of course, and do not constitute material or preferredaspects of the inventions disclosed herein. Further, the exemplary FIG.1 and other figure depictions contemplate any processing occurringbefore or after the depicted flowings, including any additionalprocessing intermediate the respective gas pulses, unless such isspecifically precluded by the particular claim under analysis asliterally worded, without interpretative or limiting reference to thebackground art description, remaining portions of the specification orthe drawings, and yet in accordance with the doctrine of equivalents.

In the course of one or both of the above-described precursor flowings,some material may adhere to a chamber internal component surface. In thecontext of this document, a “chamber internal component surface”comprises any surface of hardware received within the deposition chamberthat is subjected to multiple processings of semiconductor substrateswithin the chamber. Examples include an actual internal wall surface ofthe chamber, a surface of a chamber liner apparatus which forms adeposition subchamber within the chamber, and a surface of a portion ofa substrate support received internally of the chamber walls.

By way of example only, the adhering material might be derived totallyor at least primarily from a deposition precursor flow which forms theintermediate composition monolayer. Alternately by way of example only,such material might be derived totally or at least primarily from adeposition precursor flow which reacts with the intermediate compositionmonolayer and forms the desired deposited composition. The adheringmaterial and the intermediate composition might be of a commoncomposition relative one another or of different composition. Thematerial might also adhere to the substrate within the chamber which isthe focus of the deposition, although the invention is principallydirected to contending with material which adheres to chamber internalcomponent surfaces. Further by way of example only, and during theformation of the intermediate composition monolayer, intermediatereaction by-product might be formed, for example in any of gaseous,liquid and deposited states. Such adhering material might be of commoncomposition with one or more of the intermediate reaction by-products,or be different in composition from all intermediate reactionby-products.

In one non-limiting consideration, such adhering material might bereactive with one or a multiple of the deposition precursors. In suchevent, it might be desirable to remove such adhering material from thesubstrate so it will not react with subsequent flowing precursor, or atleast in some way passivate such adhering material to preclude itsreaction with subsequently flowing deposition precursors. Further by wayof example only, the adhering material might result, in part, from thereaction of deposition precursor with material of the chamber internalcomponent surface, thus forming material adhering thereto. Such mightconstitute a monolayer or eventually considerably thicker layers fromthe successive formation of repeated monolayers.

By way of example only, an exemplary adhered material might compriseoxygen atoms adhering to a metal internal surface of a depositionchamber. Such could manifest by the feeding of ozone in any of theabove-described exemplary processes involving the deposition of Al₂O₃.Alternately by way of example only, such might encompass any of TiCl₂,TiCl₃ and NH₃ complexes with respect to TiCl₄ and NH₃ depositionprecursor flows.

After forming at least the initially desired deposited composition ofthe layer being formed, a reactive gas is flowed to the chamber which isdifferent in composition from the multiple different depositionprecursors effective to react with the adhering material. Further in onepreferred embodiment, such reactive gas flowing preferably occurs priorto forming any further monolayer on the substrate.

In one aspect, the reactive gas reacts to modify the composition of theadhering material, with such modified composition material adhering tothe chamber internal component surface(s). By way of example only, andwhere the adhering material comprises TiCl, TiCl₂ and/or TiCl₃, anexemplary reactive gas would be O₂ to modify the adhering materialcomposition to TiO₂, which still adheres to the chamber internalcomponent surface.

In one aspect, the reactive gas reacts to effectively remove the adheredmaterial, and any reaction by-product thereof, from adhering to thechamber internal component surface. For example and by way of exampleonly, where the adhering material comprises TiCl, TiCl₂ and/or TiCl₃, anexemplary reactive gas includes Cl₂, which would effectively etch orotherwise vaporize the adhering material from the substrate (i.e., toTiCl₄) and be exhausted from the chamber.

In one aspect, the reactive gas is not capable under conditions of thereactive gas flowing of reaction with the desired deposited composition.In one aspect, and under conditions of the reactive gas flowing, thereactive gas is capable of reaction with the intermediate composition,and regardless of whether any intermediate composition is exposed duringthe reactive gas flowing, either on the substrate or on any chamberinternal component surface.

The conditions (i.e., temperature, pressure, flow rate, etc.) of thereactive gas flowing can be optimized by the artisan and are nototherwise particularly germane or preferred to any aspect of theinvention. By way of example only, such conditions might be the same as,or different from, any of a first precursor gas flow, a second precursorgas flow and/or inert purge gas flow. In one aspect, the reactive gasflow is plasma-enhanced, for example either by plasma generation withinthe chamber, plasma generation remote of the chamber, or both.

The particular reactive gas selected, whether a single constituent or amixture of constituents, will depend as a minimum upon at least someportion or component of the adhering material which will be capable ofreaction with the reactive gas under conditions of the reactive gasflowing. By way of example only, possible reactive gases componentsinclude Cl₂, O₂ and H₂. For example and by way of example only where theadhering material comprises oxygen atoms, such might be removed in thepresence of O₂ to form ozone and/or with H₂ to form H₂O which isexhausted from the chamber.

FIG. 1 depicts an exemplary such reactive gas flowing in the form of adiscrete pulse RG. After the reactive gas flowing, the sequentialforming is repeated, whereby an intermediate composition monolayer isformed, then a desired deposited composition from reaction with theintermediate composition collectively from flowing multiple differentcomposition deposition precursors to the substrate within the depositionchamber. FIG. 1 depicts such exemplary processing by subsequent P1 andP2 pulsings. In one preferred embodiment, thereafter the reactive gasflowing is repeated (FIG. 2). Further in one aspect, the repeating ofone or both of the sequential formings, as just so stated, and/or thereactive gas flowing, are sequentially repeated multiple times. Furtherin one aspect, the invention contemplates repeating the sequentiallyforming multiple times and repeating the reactive gas flowing onlyperiodically after a plurality of consecutive sequential formingrepetitions. In other words, such reactive gas flowing does notnecessarily occur intermediate each desired deposited compositionmonolayer forming, but rather after multiple formings thereof.

Further more typically and preferably, inert gas flows are interposedbetween some or all of the respective deposition precursor and reactivegas flowings. By way of example only, such is depicted in FIG. 3. Thereillustrated is a two-sequence repetition, with inert gas flows beingindicated by IN and which are interposed between the respectiveprecursor and reactive gas flows.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of atomic layer deposition of materials on a substratewithin a deposition chamber, comprising the acts of: alternatelyintroducing a first precursor and a second precursor into said chamber,wherein said first precursor forms a first layer on said substrate, andwherein said second precursor is different from said first precursor andforms a second layer on said substrate, wherein a residue is formedwithin said chamber; interrupting said alternating introduction of saidfirst and second precursors to purge said chamber, wherein said purge ofsaid chamber is performed by introducing a third gas which is reactivewith said residue, and wherein said purge removes at least a portion ofsaid residue from said chamber; and resuming the alternately introducingthe first precursor and second precursor into said chamber.
 2. Themethod of claim 1 wherein said alternating introduction of said firstand second precursors is interrupted at periodic intervals.
 3. Themethod of claim 2 wherein said periodic intervals comprise after eachintroduction of said second precursor.
 4. The method of claim 1 whereinsaid second layer reacts with said first layer to form a layer of adesired composition.
 5. The method of claim 1 wherein said third gas isdifferent from said first gas and said second gas.
 6. The method ofclaim 1 wherein the third gas comprises Cl₂.
 7. The method of claim 1wherein the third gas comprises O₂.
 8. The method of claim 1 wherein thethird gas comprises H₂.
 9. The method of claim 1 wherein the residuecomprises oxygen atoms.
 10. A method of forming material layers on asubstrate within a deposition chamber, comprising the steps of:sequentially introducing multiple precursors into said chamber andflowing said precursors. to an exposed surface of said substrate, eachprecursor being sufficiently reactive with the exposed surface of saidsubstrate at the time each said precursor is flowed to said substrate toform a new exposed surface of a different composition than prior to thetime each said precursor was flowed to said substrate, wherein duringsaid step of sequentially introducing different precursors into saidchamber a material is formed on internal surfaces of said chamber; andat least once during said step of introducing multiple precursors,interrupting the introducing of said precursors to purge said chamber,wherein said purge includes the flowing of at least one gas through saidchamber, said gas selected to be reactive with said material on internalsurfaces of said chamber, and wherein said flow of said selected gasthrough said chamber removes at least a portion of said material fromsaid internal surfaces of said chamber, and wherein after said purgestep is completed, said sequential introducing step is resumed.